Thursday, August 12, 2010

Climate change has affected winds over the Southern Ocean and reduced the amount of carbon that oceans absorb to slow global warming – a vicious cycle that has been reproduced in a high-resolution computer model for the first time.

According to a paper published in Nature earlier this year, Takamitsu Ito, an oceanographer at Colorado State University, and collaborators at Massachusetts Institute of Technology and Scripps Institution of Oceanography successfully simulated the carbon cycle of the Southern Ocean at a very high resolution using one of the world’s most powerful computers at NASA. The sheer size, remoteness and severe weather conditions surrounding the Antarctic continent prevent scientists from collecting enough data on site, so they must rely on computer simulations. The Southern Ocean is filled with eddies that require massive computer power to mimic in modeling.

“Our result implies that climate change can significantly influence the global carbon cycle,” said Ito, who co-wrote the paper with graduate student Molly Woloszyn. “The model calculation demonstrated that changing atmospheric winds indeed control the transport of carbon dioxide within the ocean and potentially change the rate of oceanic carbon uptake."

“Changes in oceanic carbon sink, in turn, affect the atmospheric carbon dioxide and climate,” Ito said. “This circular argument – that carbon dioxide is the cause and consequence of climate change – indicates complex interplay that governs the long-term evolution of our planet. The oceans are the major sink of atmospheric carbon dioxide helping to slow down global warming.”

Ito added that the atmosphere overlying the Southern Ocean is undergoing significant climate change. The major causes of climate change – ozone depletion and global warming – are trends likely to continue for decades to come, he said.

Since spring 2008, Ito has received a $418,000 grant from NASA and a $113,000 grant from NOAA to develop a high-resolution carbon cycle model of the Southern Ocean and turn the theory into practical suggestions for strategies to detect climate change impacts. The research contributes to the societal needs for predicting carbon sources and sinks and future atmospheric carbon dioxide concentrations.

Each year, the world’s oceans absorb about 2.2 billion metric tons of carbon generated by human activity. About 40 percent of oceanic carbon uptake happens in the Southern Ocean.

“We are concerned about this region because the carbon sink is large enough to impact the global carbon balance,” Ito said. “The rate at which the oceans absorb carbon from the atmosphere depends on a number of processes including atmospheric winds, heat content, ocean currents, sea ice and other factors in the ecosystem.”